1. Field of the Invention
The subject invention generally pertains to dock levelers and more specifically to a reduced-stress connection between a hinge and a lip of a dock leveler.
2. Description of Related Art
A typical truck loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles such as trucks and trailers. Many loading docks have a dock leveler to compensate for a height difference that may exist between the floor of the loading dock platform and an adjacent bed of a truck or trailer. A typical dock leveler includes a deck that is hinged along its back edge at or near the elevation of the floor so that the deck can pivotally adjust the height of its front edge to an elevation that generally matches the height of the rear edge of the truck bed to provide a ramp for material handling equipment.
In addition, a front hinge may pivotally connect an extension plate or lip to the front edge of the deck. The front hinge allows the lip to pivot between a stored, pendant position and an extended, operative position. In the extended position, the lip can rest upon the truck bed to form a bridge between the deck and the bed. This allows personnel and material handling equipment, such as a forklift truck, to readily move on and off the truck during loading and unloading operations.
With some dock levelers, the lip is connected to the deck in such a way that the lip can be used as a barrier to help prevent material handling equipment from accidentally driving off the edge of the deck while the deck is in its stored, cross-traffic position and no truck is parked at the dock. An example of such a dock leveler is disclosed in U. S. Pat. No. 4,920,598. With the '598 dock leveler, the lip includes a series of slots through which a corresponding series of bolts extend to fasten the lip to a deck hinge. The slots plus clearance between the underside of the lip and the hinge allow the lip to slide between a normal operating position and a raised barrier position.
When the lip is in its normal operating position and is extended to rest atop the back edge of a truck bed, tremendous stress can develop between the lip and the heads of the bolts that fasten the lip to the hinge when loads move over the dock leveler. The stress is concentrated along just a portion of the bolt head because the clearance between the lip and the hinge allow the lip to cock at a slight angle relative to the contact face of the bolt head. With the design disclosed in the '598 patent, the resulting stress concentrations require the use of heavier and/or stronger materials than would otherwise be needed.